I had heard that Pak Wahn was native to Malaysia so I was eager to see it growing while on a recent trip there. I saw it very rarely in Peninsular Malaysia (Malaya) but it was in all the markets in East Malaysia ( Sarawak and Sabah on the island of Borneo). It seemed that it was especially grown by the Aboriginal people of the Borneo forest as I saw many plots of Pak Wahn growing near their homes. I expect that it is a native to their forest as it is a bush that will grow in part shade.
My Pak Wahn shrub started out in a large container but the roots are well into the ground now. I have seen it grown as a short hedge as well as individually. It is a fairly easy plant to grow from semi-woody cuttings. You will also find volunteer babies coming up from the roots of mature shrubs that can be cut away with part of the root and potted up. A bit of high nitrogen fertiliser and watering during dry weather will keep it growing well.
To harvest the leaves and the soft tip stems for eating you need young fresh growth so the one bit of work you need to do every few months is to hard prune the bush. In a month or so you will have lots if young growth to harvest. The more the shrub is pruned, the more it forms new branches and so expands its output. If the bush is not kept trimmed it will grow several feet high but keeping it at about 3-4 feet makes for easy harvesting.
Pak Wahn has good nutritional value. A half cup (100 g) of fresh leaves provides 4.9 g of Protein, 51 mg of Calcium, 2.7 mg of Iron, 1122 IU of Vitamin A and 83 mg of Vitamin C. You can see that this is a good plant to let the kids pluck and chew on the leaves whenever they are out in the garden.
The leaves and soft shoots have quite a pleasant flavor. Rather like eating snow peas. Everybody that I introduce the leaves to say, "Oh, I can eat that. It tastes nice." The young fresh leaves go well in a garden salad. I usually mix them in with a base of romaine lettuce and then add some other colorful vegetable in such as orange bell peppers. The older leaves are good in a stir fry but my favorite way to cook them is in a pasta. The plucked leaves are the right size so do not need cutting. I just saute them in olive oil along with garlic and grape tomatoes and then stir in the cooked pasta. You can add some cooked chicken or a can of tuna if you want a meat meal.